1D Measurement of sodium ion flow in hydrogel after a bath concentration jump

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Abstract

NMR is used to measure sodium flow driven by a 1D concentration gradient inside poly-acrylamid (pAA) hydrogel. A sodium concentration jump from 0.5 M NaCl to 0 M NaCl is applied at the bottom of a cylindrical pAA sample. The sodium level and hydrogen level are measured as a function of time and position inside the sample for 5 days. Then a reversed step is applied, and ion flow is measured for another 5 days. During the measurement, the cylindrical sample is radially confined and allowed to swell in the axial direction. At the same time, sodium and moisture in the sample are measured on a 1D spatial grid in the axial direction. A quadriphasic mixture model (Huyghe and Janssen in Int J Eng Sci 35:793, 1997) is used to simulate the results and estimate the diffusion coefficient of sodium and chloride. The best fit results were obtained for D Na + =1.15×10 -5 cm2/s and D Cl - =2.15×10 -5 cm2/s, at 25 degrees centigrade. Different time constants were observed for swelling and deswelling.
Original languageEnglish
Pages (from-to)1706-1711
Number of pages6
JournalAnnals of Biomedical Engineering
Volume43
Issue number7
DOIs
Publication statusPublished - Jul 2015

Keywords

  • Na-NMR
  • Polyacrylamide
  • Deformation-diffusion coupling
  • Quadriphasic model

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